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Wednesday, April 21, 2021

R’EVO’lution on the Tube

London Underground is an integrated system with both rolling stock and infrastructure under the control of one operator. In fact, it can be thought of as being several systems as the deep lines are almost independent. There are some crossovers, used to move engineering trains about, but for all intents and purposes they operate separately. This means that planning can also be integrated. Rolling stock upgrades can be coordinated with improvements to the track and signalling systems to obtain a complete result.

And that planning for the tube’s future is going on right now which is why the rail engineer visited London Underground’s headquarters to talk with Director of Capital Programmes David Waboso and his key engineers – George Clark, the directorate’s Head of Engineering, and Malcolm Dobell, Head of Train Systems Engineering. Between them, they have come up with a plan to take the Underground forward to 2030, and it starts almost immediately. As George Clark said, “It’s never too soon to plan for the future.”

Radical design

For passengers, the most noticeable part of the plan will be the trains. While the new S-stock for the Victoria line is still being delivered by Bombardier, the design of the next generation is already taking shape. And it’s a radical departure from what has gone before.

The newest arrivals are just the latest development of the iconic 1938 tube stock developed by W S Graff-Baker and his team. Under-floor equipment and compact traction motors distributed down the train’s length were pioneered in the Thirties and although the S-stock is lighter and more efficient, it bears a striking resemblance to those pre-war trains.

While not exactly starting with a clean sheet of paper, Malcolm Dobell’s proposals for the next generation certainly represent a significant shift. Every aspect of the design has been considered, and then reconsidered. The result is a train named ‘EVO’.

The most striking aspect of its design is that there are no longer two bogies on each car. Articulation has allowed some of the bogies to be removed which, at over 4 tonnes each, is a lot of weight. However a conventional articulation would have positioned the remaining bogies directly under the connections between the cars. As space is so restricted in the tube, this would have prevented the inclusion of through gangways so an offset design was chosen instead whereby every bogie is completely under the end of one car, with the next suspended from it. Articulation causes difficulties with the cars’ throw on curves so each one will be shorter than at present. A current seven-car Bakerloo line set will be replaced by a nine-car EVO but, even so, it will only have ten bogies instead of 14 as at present.

There will be other weight savings too. Composite materials will be used in many areas and investigation is still going on as to whether permanent magnet motors will provide even more energy efficiency. Coupled with less weight, it is expected that this would bring a significant reduction in ducting and number of cooling fans required on the infrastructure to keep tunnel temperatures under control.

EVO design artists impression
Artist's impression of the EVO design

Fewer bogies, more room

The shorter cars bring another benefit. The rotation of each bogie will be reduced, especially if a shorter wheelbase design is adopted. Currently the optimum diameter of the wheels is 700mm – this means they protrude into the cabin. That’s the reason why seats over the bogies are set in towards the centre of the car a little, with a small box-section beneath them – the wheels are under that box and the seats. Have a look next time you’re on the tube. With reduced rotation, the seats can be moved a little further back to give greater gangway width – a small but significant increase.

Doors will still slide. Plug doors have been discussed but no manufacturer is currently able to guarantee the reliability that London Underground needs given the sheer number of times they open and close each day. And of course plug doors impinge on crowded platforms so that could also be an issue. However, they will all be double-doors and possibly slightly wider (1800mm) than at present (1600mm). The door operating mechanisms will also be moved up into the roof.

So with open gangways, wider doors and increased distances between rows of seats, the EVO will feel lighter and airier than today’s trains, with about 10% more capacity. They will also of course be fitted with all the latest passenger information systems, CCTV and so on. However those aren’t the only changes. The trains will also be air-conditioned.

EVO typical motor
A typical permanent magnet motor

Cooling

Cooling the deep tube has, until now, been a Holy Grail – everyone’s ambition but physically impossible. However, the new plans have come up with a practical solution.

Firstly, it’s not the tunnels and stations that are being cooled – just the trains. Secondly, the Underground is effectively a closed thermal system. The air conditioning process doesn’t increase the amount of heat, it just moves it around. What would add heat is the energy that’s used to run the aircon as any input of energy increases the overall heat in the system. But lighter, more efficient trains use significantly less energy and some of that generated by the train during braking will be harnessed to power the air conditioning, helping to ensure that the upgrade uses no more energy than is consumed today – the stated objective.

Suddenly cooling the tube is possible. What had been estimated to be a £100 million project – just to cool the Bakerloo line alone – can now be done for less than £10 million thanks to the energy savings made from running the trains. Granted, the temperature may go up a little in localised areas but that can be managed.

And it’s going to happen sooner than you think. The first of the new EVOs should be in service – either on the Waterloo & City line or the Bakerloo – around 2016. Because of all the new technology involved, that means that prototypes will have to be running in 2015 and ordered in 2012. London Underground has already held discussions with potential suppliers so things are moving apace.

Of course, shiny new trains aren’t the total solution to moving more people, more quickly. They make the journey a more comfortable experience but, as platforms can’t be lengthened, the only way to increase capacity is to run more trains, and that means improving the signalling as well.

From fixed to moving

Currently, London Underground uses a fixed-block system. Traditionally these have been quite long, requiring significant gaps between trains. In 1968, the Victoria became the first line to use a ‘modern’ signalling system – Automatic Train Operation – with shorter blocks. The newer system on the Central line has shorter blocks still, but they remain fixed, whilst the recent Victoria upgrade has resulted in its being compressed even further.

Moving blocks are the answer. Trains will be in constant communication with the system controller which will calculate stopping distances and safety margins, controlling the separation between trains but minimising the gaps to allow them to run more frequently.

Trials are taking place on the Jubilee line. These have progressed so they can now be tested in service, with full implementation later this year. The Northern line will be next, with moving block signalling going in for 2014. This change alone can increase capacity on a line by 20-30%.

EVO close up
A close-up look at the new EVO design

Timescale

Of course, changes can’t be made overnight – David Waboso’s plans go forward to 2030. Although they are subject to change, current thinking is that the Bakerloo will be upgraded in 2017/2019, the Piccadilly 2019/2022, the Central by 2025, the Northern by 2027 and the Jubilee line around 2030. The Victoria, for which the S-stock is still being delivered, will be the last to change.

With the new signalling and EVOs, together with some infrastructure work to remove pinch-points, London’s tube system will be able to run 30 trains an hour on each line in each direction. That’s a train entering the platform every two minutes!

And there are other plans in place covering other aspects of the deep tube. Several new vents will be driven to help remove more of the excess heat. Platforms are to be ‘humped’ at some locations to improve disabled access. Farringdon, Tottenham Court Road, Victoria and King’s Cross stations will be remodelled to benefit passenger flows. But the most obvious change will be those new EVO trains – more of a rEVOlution than an EVOlution.

5 COMMENTS

    • They will have much shorter carriages (this is a requirement for walk-through trains) – so less doors in each one. Obviously the number of carriages will go up too.

  1. Awesome train!

    However, do NOT call something “impossible” when it is already been proven SCIENTIFICALLY that there is a method to achieve something.

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